High Tg, Nonpoled Photorefractive Polymers

Room-temperature photorefractivity without prepoling was demonstrated in polymers and copolymers with a glass transition temperature well above 100 degrees C. The compounds used are multifunctional side-chain polymers exhibiting chiral, semiconducting, photochromic, and nonlinear optical (azoaromatic moieties) properties. The photorefractive performance was linked to the reorientational effect of the photogenerated space-charge field, which well below the glass transition temperature can be active in the presence of the conformational mobility achieved via the trans-cis light-induced isomerization. The grating build-up time, which is long at lambda = 633 nm (with a time constant tau approximate to 500-1000 s) decreases by 2 orders of magnitude at lambda = 532 nm, where absorption is higher.